1. Field of the Invention
The present invention relates to a novel force feed back supply apparatus, and particularly to a technique for preventing an undesirable load from being imposed on an operator when a force feed back is not supplied.
2. Description of the Related Art
There is known a force feed back supply apparatus for enabling an operator to have the touch as if the operator touches a real object or feel the resistance as if the operator operates a real object when the operator touches or operates a virtual object in a virtual space.
According to a conventional force feed back supply apparatus, a portion which is held by or mounted on an operator is linked to a force feed back generating unit for generating a force feed back such as a robot at all times. Therefore, even if no force feed back is supplied, the operator feels the mass (inertial force) of the force feed back generating unit or the frictional resistance of the force feed back generating unit when the operator is about to move his/her arms or the like, and this makes the operator uncomfortable.
In order to avoid this problem, there may be considered a method for miniaturizing the force feed back generating unit at maximum or reducing the frictional resistance of the movable portion. However, this method inherently causes the performance of the force feed back supply apparatus to be dependent on the ratio (output/size) of an actuator. Particularly for an arm type force feed back supply apparatus which is required to supply large force, there does not exist any actuator which can provide a sufficient ratio (output/size).
There is also known a method in which a force sensor is provided between an operator holding portion and a robot portion and the robot is actively controlled on the basis of the signal from the force sensor, thereby reducing the uncomfortableness of the operator. However, it is impossible to perfectly extinguish the uncomfortableness of the operator in this method because delay necessarily occurs in the control loop.
Furthermore, Japanese Patent Laid-open No. 257947/1996 and Japanese Patent Laid-open No. 109070/1997 disclose other methods which do not make any operator feel uncomfortable because the operator is not restrained. According to these methods, an object model used to give a force feed back to an operator is prepared in advance as means for supplying the force feed back and the operator touches his/her finger to the object model. Therefore, when repulsive force from objects having different shapes in the virtual space is supplied, actually existing object models for these objects must be prepared, resulting in complication of the apparatus itself.
Therefore, an object of the present invention is to provide a force feed back supply apparatus which can prevent an operator from suffering an undesirable load when any force feed back is not supplied.
In order to attain the above object, according to the present invention, a force feed back supply apparatus having a force feed back supply unit which is held by or mounted on an operator, and a force feed back generating unit for providing the force feed back supply unit with the load corresponding to an operation or the like of the operator, is characterized by comprising: a clutch mechanism interposed between the force feed back supply unit and the force feed back generating unit; detection means for detecting the position and orientation (attitude) of the force feed back supply unit with respect to the force feed back generating unit; and a controller for controlling the force feed back generating unit on the basis of the detection result of the detection means, etc., wherein when a force feed back is supplied, the clutch mechanism is set to be coupled between the force feed back supply unit and the force feed back generating unit, and when no force feed back is supplied, the clutch mechanism is set to be uncoupled between the force feed back supply unit and the force feed back generating unit and the controller controls the force feed back generating unit on the basis of the detection result of the detection means so that the relative position between the force feed back supply unit and the force feed back generating unit is kept fixed at all times.
Accordingly, according to the force feed back supply apparatus of the present invention, since the force feed back supply unit and the force feed back generating unit are mechanically separated from each other when no force feed back is supplied, the operator can be prevented from suffering a vain load due to the inertial force, frictional resistance or the like of the force feed back generating unit.